Flute grinding apparatus



p 1941- A. A; HERRICK ET AL 2,257,255

FLUTE GRINDING APPARATUS Filed May 28, 1958 9 Sheets-Sheet 1 INVENTORS g ALBERT AHEREICK EARL ,e. KOO/V2 AQTTORNEYS sna ;30,1941; HERRI CK ETAL k 2,257,256,

FLUTE GRINDING APPARATUS Filed May 28, 1938 9 Sheets-Sheet 2 N VE NTO RS \3 ALBERT AHEEEIcK E1921. ME. K00/VZ ATTORN EYS 4 Sept. 30, 1941. A. A. HERRICK ET AL FLUTE GRINDING APPARATUS Filed May 28, 1958 H Q -SheetSP-Sheet :s

M IIYIIQIIU ATTO R N EYS EARL E. KOO/VZ \NVENTORS ALBEET A. HERk/CK Sept. 30, 1941. A. A. HERRICK ET AL 2,257,256 FLUTE GRINDING APPARATUS Filed May 28, 1938 9 Sheets-$heet 5 Sept. 30,1941,

A. A. HERRICK ET AL FLUTE GRINDING APPARATUS v 9 Sheets-Sheet 6 Filed May 28, 1938 HEBk/CK EAEL E. KO0NZ INVENTORS BERT A.

ww a BY QZMW M ATTORNEYS p 1941- A; A. HERRICK r-rrm. 2,257,256

FLUTE GRINDING APPARATUS I Filed May 28, 1938 9 Sheets-Sheet 7 INVENTORS ALBERT A. HEER/CK EARL B. KOONZ ZMW ATTORNEYS p 30, 1941. v A. HERRICK. ET AL 2,257,256 FLUTE GRINDING APPARATUS Filed May 28, 1938 9 Sheets-Sheet 8 NTORS EARL EJ600172 WW INVE ALBEB ATTO RN EYS Sept. 30, 19.41. A. A. HERRICK ET AL 2,257,256 7 FLUTE GRINDING APPARATUS 7 Filed May 28, 1958 9 Sheets-Sheet 9 IIIIIIHH'" HUM INVENTORS ALBEBT 14. HEEEIE'K EARL E. KOONZ ATTORNEYS Jll HDHHUIWU.

Patented Sept. 30, 1941 FLUTE GRINDING APPARATUS Albert A. Herrick and Earl R. Koonz, Greenfield, Mass., assignors to Greenfield Tap and Die Corporation, Greenfield, Mass, a corporation of Massachusetts Application May 28, 1938, Serial No. 210,563

10 Claims.

This invention relates to improvements in apparatus of a type adapted for use in grinding auxiliary flutes and the like in thread cutting taps, the auxiliary flutes forming continuations of the standard flutes and extending at an angle thereto toward the entrance end of the tap.

A purpose of the invention is to provide apparatus that will form such auxiliary flutes with a high degree of precision, and adapted for rapid and convenient positioning and removal of taps of different sizes.

The invention is particularly applicable to the generation of auxiliary flutes axially offset from the tap axis, this type being sometimes referred to as gun flutes. A feature of the invention is the provision of apparatus for generating such flutes with precision at a predetermined angle to the tap axis and offset from such axis by a selected distance, as well as to provide means for conveniently altering such angle, oflset spacing, or both.

Another object is to provide apparatus of the indicated type in which the auxiliary flute is ground by reciprocation against a grinding wheel having a suitably contoured tap-engaging face; to maintain the desired contour of such face; and to compensate for changes in the diameter of the wheel.

A further feature is the provision of automatically operated tap feeding and reciprocating means, together with means for halting the tap hoder in shifted loading position upon completion of grinding and for resuming the grinding operations after loading or resetting.

Other objects and advantages will appear from the following description considered in connection with the accompanying drawings, in which Fig. 1 is a front elevation of the apparatus in loading position showing the fluid pressure and cooling systems;

Fig. 2 is an end view of the entrance portion of a tap showing a gun flute;

Fig. 3 is a side elevation thereof;

Fig. 4 is an enlarged front elevation of the grinding apparatus shown in Fig. 1, in grinding position;

Fig. 5 is an end view of said apparatus also in grinding position;

Fig. 6 is a horizontal section on line 6-6 of Fig. 5 with parts broken away, showing the carriage-actuating mechanism in plan;

Fig. '7 is a vertical section on line 1'! of Fig. 6 showing the carriage and the front portion of the actuating mechanism;

Fig. 8 is a perspective view of the carriage slide and tap holder;

Fig. 9 is a detail of the tap registering finger;

Fig. 10 is a longitudinal vertical section on line I 0--l0 of Fig. 6 showing the carriage and piston in section and the rear portion of the actuating mechanism;

Fig. 11 is a reduced fragmentary plan of the grinding wheel, truing device and associated parts;

Fig. 12 is a vertical section through the carriage reciprocating valve similar to Fig. 7 but showing the valve in reverse position;

Fig. 13 is a vertical transverse section on line I3l3 of Fig. 6 showing the left-hand portion of the carriage actuating mechanism;

Fig. 14 is a section on line l4--I4 of Fig. 6 showing the right-hand portion of the actuating mechanism;

Fig. 15 is a front elevation similar to Fig. 4 showing a hand-operated type of machine; and

Fig. 16 is a side elevation of said hand machine.

The apparatus in the form illustrated in Figs. 1 to 14 herein includes in general a stationary grinding wheel; a carriage on which the tap is mounted in position for grinding; an arrangement for reciprocating the tap against the grinding wheel and feeding the tap toward the wheel for a predetermined distance. arranged to halt the reciprocation and shift the carriage to a loading position at the end of the grinding operation; a liquid pressure feed for operating the carriage through a suitable hydraulic valve; an arrangement for circulating a coolant, and suitable shields for protecting the operator and preventing splash.

Referring to Figs. 1, 4 and 5, the apparatus includes a frame 20 supporting a flat disc grinding wheel 2|, mounted on a shaft 22 extending Examine! through a suitable journal 23 on frame 20 and carrying at its rear end a pulley 24 driven through belt 25 by motor 26 fixed to bracket 21 pivoted at 28 to frame 20 and held in adjusted position by screw 29 bearing against the frame for adjustment of belt tension.

Grinding wheel 2| is surrounded by a housing 30 provided at its rear with a horizontal slide extension 3| mortised into a guideway in bracket 32 mounted on the top of frame 20. As shown in Fig. 11, an adjusting screw 33 threaded into the rear of grinding wheel housing 30, is journaled in ear 34 on bracket 32 and carries index wheel 35 registering with pointer 36 on said bracket. The housing 30 has a removable face plate 31 and is open at the bottom. It may be provided with a splash guard 38 mounted in a vertical slot by screw 38 for suitable adjustment. The wheel shaft passes through a slot 88 in the rear of housing 38 permitting adjustment of the housing.

The periphery of grinding wheel 2| has a semicircular contour in cross section; and a suitable arrangement is mounted on housing 38 for truing such surface. This arrangement includes a cylindrical body 8| journaled in a suitable hub 82 formed on housing 38 and provided at its upper end with an enlarged head 83 having a handle pin 88 projecting laterally therefrom. The lower end of the body carries a diamond pointed stud 85 adJ'ustably held in position by clamp 85 and arranged with the diamond point spaced from the axis of rotation of body 8| by a distance equal to the radius of transverse curvature of the outer face of wheel 2|.

The carriage and operating mechanism are formed as a movable unit mounted on a vertical slide 58 formed on the frame 28 and engaged by suitable-mortised guideways I on said unit. An arrangement is provided for manual vertical adjustment of the unit, and includes elevator screw 52 journaled in a bearing column 53 mounted on frame 28. A hand wheel 58 is fixed to the upper end of screw 52 and carries a scale 55 cooperating with an indicator 55 on the column 53.

An elevator nut 51 threaded on screw 52 is vertically slidable in channel 58 formed in the slide 58 and supports the housing 58 on which the tap holding carriage and the operating mechanism therefor are mounted.

The carriage unit includes a frame 55 having end skirts 55 slidably engaging front round guide rod 51 and rear square guide rod 58 mounted in cylinder blocks 58 and 18 carried by the housing 58. Piston rod 1| fixed to the left-hand skirt 55 passes through a suitable gland in the head 12 of cylinder 13- mounted at its ends in the blocks 58, 18, and is connected to piston 18 in said cylinder.

Cylinder block 58 is provided with a suitable bore 15 communicating with the end of the cylinder and connected to valve line 18. The opposite end of cylinder 13 is also connected through head 11 and line 18 with valve 18 located in housing 58. The valve comprises a body 88 and a rotary plug 8| fitted therein. The body 88 is provided with a passage 82 communicating at its ends with the plug and connected to the fluid outlet 83. It also has a corresponding lower passage 88 communicating at its ends with plug 8| and connected to the fluid inlet 85. The valve lines 18 and 18 are connected by passages 88 through the body to the plug, each located between the ends of passages 82 and 88. The plug 8| has recesses 81 at opposite sides in register with the adjacent passages 88 and the ends of passages 88 and 82, arranged to overlap and connect each passage 85 with the end of either passage 82 or passage 88 when plug 8| is in right-hand or left-hand position, and to communicate only with passages 88 when the plug is in central position.

The fluid passages 83 and 85 are connected to suitable sources of fluid pressure and discharge. The piston may be operated by oil supplied from a reservoir 88 through pump 88 and feed pipe 88 connected to the inlet 85 of the valve 18, the outlet 83 of the valve being connected through return pipe 8| with the reservoir 88.

Suitable mechanism is provided for oscillating valve plug 8| at suitable intervals to reverse the oil feed connections to cylinder 13 and thereby to reciprocate the carriage frame 55. In the f rm illustrated the valve plug 8| is provided with a stem 82 (Fig. 14) extending through the front of the housing 58 and carrying valve lever 83. Lever 83 is provided with a fork 88 traversed by a pin extending through slot 85 of valve link 81. The opposite end of link 81 is pivoted on pin 88 carried by control lever 88 (Figs. 4, 13). Sumcient play is provided between link 81 and pins 85, 88 to permit the axial shifting of lever 88 as hereinafter set forth.

Control lever 88 is fixed to the outer end of the control lever shaft I88 J'oumaled for oscillation and longitudinal movement in the front and rear skirts of housing 58. An arrangement is provided for oscillating lever 88 by engagement with suitable abutments on the reciprocating carriage frame 55. In the arrangement illustrated, frame 55 is provided with a T-slot in which drive dogs I82 and I 83 are adjustably mounted by suitable bolts I88 having heads fitting in slot IIII. The upper end of control lever 88 is provided with a drive blade I85 positioned to engage dogs I82 and I83 during grinding. Means may be provided for locking the parts in inoperative position, such as the lock plunger I85 carried by the lower end of valve lever 83, pressed outwardly by spring I81 into socket I 88 in housing 58 arranged to hold lever 83 in vertical neutral position. Plunger I85 is held in retracted position during operation as by cross pin I88 which may by rotation be located either in slot I88a or on the side walls of the slot.

Means is provided for shifting the carriage frame 55 to loading position at the left and for halting the reciprocation of the carriage when said frame is in loading position. In the drawings this includes a stop dog II8 adjustably mounted in slot I 8| and positioned to engage a stud III on stop slide II2 mounted on studs I I3 on housing 58 passing through slots I I8 in slide II2 to permit horizontal shifting of the slide. A valve shifting stud II5 on slide H2 is positioned to engage a stop lug II5 on the upper end of valve lever 83 arranged to shift the valve into neutral position, with recesses 81 in register only with passages 88, when slide H2 is fully shifted to the left, the positioning of valve lever 83 operating through link 81 to move control lever 88 likewise to central approximately vertical position. An arrangement is provided for limiting the period of reciprocation of the carriage, operative at the end of the predetermined number of reciprocations to shift control lever 88 outwardly by axial movement of its shaft I88, so that the control lever blade I85 will clear the shorter dog I83 during the movement of the carriage to the left. For this purpose the control lever 88 is provided at its lower end with a roller I 28 (Figs. 4 and 5) engaging the lower cam face of ratchet lever I2I pivoted on the housing 58. Ratchet link I22 pivoted to lever I2I has a slot I23 engaging stud I28 on ratchet arm I25 carrying pawl I28 pressed by spring I21 into engagement with ratchet I28. Ratchet arm I 25 is biased up wardly by spring I28 connected to block I38 mounted on the housing 58 and carrying a stop screw I3I engaging the upper face of arm I25 to regulate the throw of the pawl. Ratchet lever I2I is also biased upwardly by spring I32 connected to block I38.

The lower face of ratchet lever I2I engaging roller I 28 is provided with depressions I33 and I38 engaging roller I28 when control lever 88 is in right and left hand positions, and an inter- Di. ABHAUlNkJ.

mediate elevation I35 engaging roller I to depress pawl I26.

Ratchet I23, which preferably is provided with a large nu'fi iber of relatively fine teeth to permit a wide range of adjustment of the throw, is mounted on ratchet shaft I36 journaled in the front and the rear of housing 59; and ratchet arm I may conveniently be journaled on shaft I36. Shaft I36 and control lever shaft I00 carry mechanism for shifting the control lever shaft I00 axially to arrest the reciprocation of the carriage. For this purpose a pawl arm I31 fixed on shaft I00 within housing 59 carries a pawl I38 (Figs. 7 and 13) biased upwardly by spring I39 and engaging a partial ratchet I40 fixed to shaft I36. Ratchet I40 is provided with two teeth MI and I42 having a relatively wide spacing, the face I43 of ratchet I40 beyond these teeth being smooth. Also fixed to shaft I36 is the cam disc I44 provided with a face cam I45 (Figs. 6 and 10) shifting the carriage upwardly toward the grind- 1 ing wheel 2I during grinding. In the form illustrated, this arrangement shifts the entire operating mechanism carried by housing 59, and

provides an automatic vertical feed in combination with the manual vertical feed through operi ation of hand wheel 54. This arrangement includes a feed lever I (Figs. 6 and 10) pivoted on stud I56 on the housing 59 and provided with a fulcrum stud I51 bearing against a lug I58 on elevator nut 51. The opposite end of lever I 55 carries a pin I59 bearing against the outer face I60 of cam disc I44 which has a helical contour arranged to force pin I59 downwardly as the ratchet shaft I36 is revolved, thereby lifting the housing 59 and the entire operating mechanism carried thereby. The ends of the helical face I60 are connected by a step ISI for dropping the housing 59 and associated parts to starting position.

A suitable mounting arrangement for supporting and adjusting the tap is carried by carriage frame 65. The frame is provided near its left end with a carriage mounting (Figs. 4, 5 and 7) including a transverse slide I mortised into a guideway in carriage I66.

I61 (Fig. 5) is threaded in the carriage I66 and passes through retaining plate I68, being held against longitudinal movement by the hub of knob I69 and collar I10 on screw I61 bearing against opposite sides of plate I68.

Carriage I66 includes flanges I1I between which the mounting frame I12 i clamped by aligned screws I13. The frame I12 is recessed at the top to receive an interchangeable tap cradle block I14 having a bore I15 fitting a tap I16 of a given diameter. The block I14 shown in the drawings is particularly adapted for gun flute grinding, and is cut away from top center through about 90 degrees to the left, being held in place by clamping screw I11.

An arrangement is provided for locating and holding the tap accurately in the desired rotated position, and is particularly advantageous when grinding gun flutes, being adapted to locate the standard flutes in accurate registration with the An adjusting screw Examiner flute that is ground by the wheel 2|. For this purpose an indexing rocker arm I18 pivoted in frame I12 is provided with an indexing finger I19 (Fig. 9) having a shank I adjustably held in a socket in arm I18 by set screw I8I and provided with an offset arm I82 carrying a ball tip I83. The radius of tip I83 is preferably slightly greater than that of the standard flute I92 of the tap that is being ground, so that the tip engages symmetrically the opposite edges of the flute. Rocker arm I18 and finger I19 are biased toward the tap by a spring I84 between the rear end of the arm and the top of frame I12 with suflicient force to clamp the tap in block I14.

An arrangement is provided for adjusting the frame I12 about its axis to provide a selected angular relation between the axis of the tap and that of the gun flute I93 being ground therein. The adjustment may be made by loosening screws I13, rotating the frame I12 and then tightening said screws. An index I85 (Fig. 4) may be provided at the front of frame I12 in register with an index plate I86 mounted on the front fiange I1I.

Frame I12 is provided with means for positioning the front end of a tap I16 located in cradle block I14 in fixed longitudinal position so that flutes ground by wheel 2I may extend an equal distance along the tap. For this purpose a pivot rod I81 rotatably mounted in a longitudinal bore in carriage I 66 beneath the position of tap I16 therein carries front registering arm I88 and rear registering arm I89. Arm I88, fixed to the front end of rod I81, carries a locater plate I90 in alignment with tap I16 when arm I88 is in upper position. Rear arm I89, rotatable on rod I81 and held against carriage I66 by head I94, is provided with a registering screw I9I threaded through the arm in position to engage the rear end of tap I16.

An arrangement is provided for supplying a suitable liquid to the face of the grinding wheel. This may include a reservoir I from which the coolant is forced by pump I96 through line I91 and cock I98 to spout I99 located in position to supply wheel 2| with the liquid in the grinding zone.

The apparatus should be provided with suitable guards to prevent injury to workmen and to eliminate splashing of the cooling liquid. In the form illustrated in Figs. 1, 4 and 5 the construction includes an arcuate lower guard 200 having side plates 20I pivoted to the ends of a forked bracket 202 mounted on a face plate 203 extending upwardly from housing 59. Bracket 202 is provided with a boss 2I4 in which the coolant line to spout I99 is adjustably clamped by set screw 2I5. The forward plate 20I is provided with an extension arm 204 pivoted to link 205 having a slot 206 receiving a pin 201 on arm 208 pivoted on face plate 31 of housing 30 and carrying an arcuate guard 209. The upper end of link 205 is provided with a threaded adjusting rod 2I0 extending into slot 206 and engaging pin 201. The guards are held in operating position by a latch bar or foot 2II arranged to rest on the edge of pan 2'I2 when swung against positioning pin 2I3 on side plate 20I.

The hand-operated machine shown in Figs. 15 and 16 includes the same general arrangement of grinding wheel and carriage, but is arranged for manual reciprocation of the carriage beneath the wheel. In this arrangement the elevator screw 52 is provided with an elevator nut 51 bolted to a vertical slide frame 220 having a rear guideway in mortised engagement with the vertical slide 50. A bracket 22| on frame 220 carries parallel slide rods 22;. Carriage frame 223 is slidably mounted onYods 222, the forward rod passing through a suitable bore in frame 223 while a grooved slide plate 224 adjustably bolted to the bottom of frame 223 rests on the rear slide rod 222. Frame 223 is provided with flanges III, a cross slide I65 and associated parts, including the carriage and tap mounting, corresponding to those which have already been set forth in detail. An adjustable stop screw 2'25 threaded in the forward face of frame 223 and held in adjusted position by lock nut 226 is positioned to engage bracket 22I and limit the forward movement of the carriage during grinding.

In the operation of the automatic arrangement shown in Figs. 1-14, and starting with the parts in loading position, the guard latch bar 2 is shifted away from pan 2I2 permitting the lower guard 200 to swing beneath the carriage, the resultant shifting of link 205 permitting the upper guard 209 to swing downwardly beneath wheel 2| to protect the operators fingers. A tap I16 is inserted in a block I14 fitting the tap and clamped in frame I12 by screw IIl, the registering arms I88 and I89 are swung upwardly into alignment with the tap, and registering screw I9I is rotated until the front of the tap is positioned against locator plate I90. An indexing finger I19 having a tip I83 of proper size to engage the flutes in tap I16 is mounted in rocker arm I18 and tap I16 is rotated until tip I83 registers accurately in the flute whose continuation is to be ground. Arm I88 is swung out of the grinding path, arm I89 remaining frictionally held in vertical position to back up the shank end of the tap during grinding. The carriage I66 may be transversely adjusted by manipulating adjusting screw I61 to position the flute accurately at the proper offset distance from the tap axis.

Wheel 2| may be trued by rotating index wheel 35 until the diamond point on stud 45 engages the wheel. Oscillation of the body 4| of the truing device by oscillating handle pin 44 through a semi-circle while wheel 2| is rotating will provide an accurate semi-circular surface on the grinding wheel 2|. The index on wheel 35 may be calibrated with the scale 55 on elevator hand wheel 54, as said index indicates the diameter of grinding wheel 2| and the scale 55 indicates the elevation of the carriage and associated parts which must correspond to the wheel diameter in order to bring the tap into grinding position.

The carriage and associated parts are in loading position, with stop dog I I against stud III and valve lever 93 in central vertical position. Control lever 99 is slightly to the left of vertical position with roller I20 on the slope between depression I34 and elevation I35, and is also in outwardly shifted position as indicated 1; dotted lines on Fig. 13. Guards 200 and 209 are shifted into running position as shown in Fig. 1 and held by foot 2| I. Control lever 99 is shifted counterclockwise by depressing handle III on said lever. thereby shifting valve lever 93 through the action of link 91 in similar manner, admitting oil under pressure to the left of piston I4. The carriage and frame 65 move to the right, the shorter dog I03 passing drive blade I05 on control lever 99. Dog I02 then engages blade I05 and rocks control lever 99 to the right, throwing valve lever 93 in the same direction and reversing the valve I9.

Pawl I38 on the control lever shaft I00 is in engagement with tooth I 42 of the partial ratchet I40 when the carriage is in loading position; and the initial shift of lever 99 retracts pawl I38, rotating the ratchet shaft I36 a sufficient distance to carry cam pin I5I rearwardly over cam face I48, permitting shift lever I49 and control lever shaft I00 to shift rearwardly under the action of spring I54. The shift of shaft I00 will bring the drive blade I05 into alignment with the short dog I03, so that when the carriage is reversed dog I03 will rotate control lever 99 counter-clockwise, reversing the valve.

At the same time the oscillation of lever 99 rocks ratchet arm I 25 at each stroke, rotating rachet shaft I36 and gradually forcing downwardly the pin I59 on lever I55, thereby raising the housing 59, the carriage structure and the tap toward the grinding wheel 2|. The pawl I38 is inoperative during grinding since it rides on the unbroken outer face I43 of disc I40. The reciprocation of the tap against the grinding wheel 2| continues with gradual feed of the tap toward the wheel; and it is noted that the total depth of out can be accurately determined by correlating the total feed distance caused by the action of cam face I60 with the initial spacing of the tap from grinding wheel 2| which may be regulated by manipulation of hand wheel 54.

The reciprocation of the carriage and the feed of the tap are continued for a number of strokes determined by the throw of pawl I26 controlled by the setting of stop screw I3I. The grinding is terminated when ratchet disc I 40 has rotated to the point where pawl I38 engages tooth I. At this point cam pin I5I is approaching cam face I46. The next clockwise movement of control lever 99 will rotate ratchet shaft I 36 through the action of pawl I38 for a distance suflicient to bring cam pin |5| on to the central elevated face I41 of cam I45, rocking the shift lever I49 andforcing the control lever shaft I00 and lever 99 in a forward direction until the drive blade I05 will clear short dog I03. These operations take place as the result of a clockwise shift of control lever 99, which sets the valve I9 in position to shift the carriage frame 65 and associated parts toward the left. This action is continued until stop dog IIO contacts stud III, moving stop slide M2 to the left, the engagement of shifting stud |I5 with lug I I6 serving to move valve lever 93 into neutral position and moving control lever 99 into similar position through link 91. The carriage is now at the extreme left position shown in Fig. 1, substantially spaced from the grinding wheel 2| and ready for resetting or replacement of the tap when the guards have been shifted in the manner already set forth.

The operation of the hand machine shown in Figs. 15 and 16 involves the same general manipulationininserting and registering the tap. During grinding carriage 223 is reciprocated along slide rods 222 by hand, and is fed toward the wheel 2| by rotating hand wheel 54.

The described arrangement includes features that are particularly advantageous in grinding gun flutes in taps with accuracy, speed and convenience; but it will be apparent that certain features are suitable for use in other operations and the invention is not restricted to the specific purpose disclosed except as limited by the claims.

We claim:

1. Tap flute grinding apparatus including a grindingwheel,a tap holder, means for imparting relative movement between the wheel and the holder defining a flute grinding path, means for mounting a fluted tap in the holder with the en trance end of the tap extending into the grinding path at an angle, and means on the holder fitting into 343D flute and securely held in contact with opposite edges of the flute for maintaining the flute circumferentially in register relative to the grinding path.

2. Tap flute grinding apparatus including a grinding wheel, a tap holder, means for imparting relative movement between the Wheel and the holder defining a flute grinding path, means for mounting a tap in the holder including a tap socket and a tap positioning unit mounted on the holder including a stop member in alignment with the entrance end of the tap and means engaging the rear end of the tap for shifting the tap into contact with the stop member, the stop unit being movable out of alignment with the tap during grinding.

3. Grinding apparatus including a grinding wheel, a work holder, a support, means carried by the support for reciprocating the work holder on the support in grinding relation to the wheel, and means on the support for automatically feeding the work holder toward the wheel, said means including a stationary external bearing, a lever engaging the support and fulcrumed on the bearing, and cam means on the support rotated by the drive means for shifting the lever about the fulcrum.

4. Grinding apparatus including a grinding wheel and a feed unit including a support, a work holder, drive means for reciprocating the work holder on the support in grinding relation to the wheel, ratchet means actuated by the drive means, means for feeding the work holder in the plane of the grinding wheel actuated by the ratchet means, drive control means, and cam means for shifting the control means out of normal operating position actuated by the ratchet means.

5. Tap flute grinding apparatus including a grinding wheel, a support moving parallel to the plane of the wheel and carrying a work support moving at right angles to the direction of movement of said first mentioned support and in the plane of the grinding wheel, a work holder carried by said work support and tap holding means on said work holder adapted to position a tap in the plane of said grinding wheel, manual means for setting the position of said first mentioned support with relation to said wheel, automatic means for producing relative reciprocation between said grinding wheel and said work support, automatic means for moving said first support step by step toward said grinding wheel, and means for automatically terminating said step by step movement after a predetermined number of operations.

6. Tap flute grinding apparatus as set forth in claim 5 in which the work holder is angularly adjustable on the work support so as to position the tap at an angle to the tangent at the point of contact with the Wheel.

'7. Tap flute grinding apparatus including'a grinding wheel rotating in a vertical plane, a stationary frame, a main housing support vertically adjustable on said frame toward and away from said grinding wheel, a carriage frame horizontally reciprocable on said main housing support parallel to the plane of said grinding wheel, a work holder carried by said carriage frame and transversely adjustable by a movement in a plane at right angles to the plane of said grinding wheel to position the tap carried by said holder longitudinally in contact with said wheel, means carried by said main housing support substantially in the plane of the grinding wheel for reciprocating said carriage frame and moving the tap back and forth with its flute in contact with the periphery of the grinding wheel, and means for automatically moving said main housing support vertically by the reciprocating movement of said carriage frame so as progressively to feed the tap against the grinding wheel.

8. Tap flute grinding apparatus as set forth in claim 7 in which the reciprocating means for the carriage frame is hydraulically operated and comprises a mechanical control actuated from the carriage frame and connected to operate the means for moving the main housing support vertically.

9. In apparatus for grinding tap flutes, the combination with a grinding wheel of a. carriage adapted to support the tap in grinding position and reciprocable in the plane of the grinding wheel, means for reciprocating said carriage comprising a control lever, opposing stops on said carriage for engaging said lever to move it in opposite directions, a third stopon said carriage acting to move said lever to an intermediate neutral position corresponding to the inoperative condition of said reciprocating means, cam means for moving said lever out of the path of one of said opposing stops while maintaining its actuation by said third stop, and means for operating said cam by the reciprocating movements of said control lever so that at the end of a number of reciprocations the actuation of the control lever will be transferred to said third stop returning the lever to said neutral position.

10. Tap flute grinding apparatus as set forth in claim 9 in which the carriage is also vertically movable and the cam means for shifting the operating head also progressively moves the carriage vertically during its reciprocations so as to feed the tap against the grinding wheel.

EARL R. KOONZ. ALBERT A. HERRICK. 

